Zoom lens system with vibration reduction function

ABSTRACT

A zoom lens system with vibration reduction function includes, in succession from the object side, a first lens unit having positive refractive power, a second lens unit movable along a direction across the optical axis thereof and having negative refractive power, a third lens unit, a fourth lens unit having positive refractive power, a fifth lens unit having negative refractive power, during the focal-length change from the wide angle end to the telephoto end, the spacing between the first lens unit and the second lens unit being increased, the spacing between the second lens unit and the third lens unit being varied, and the spacing between the fourth lens unit and the fifth lens unit being decreased, and a vibration reduction device for moving the second lens unit along the direction across the optical axis, the stabilization of an image on an image plane being accomplished by the movement of the second lens unit caused by the vibration reduction device.

This is a division of application Ser. No. 08/245,033 filed May 17,1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a zoom lens system with the function ofpreventing image shake, and particularly is suitable for a photographiczoom lens system.

2. Related Background Art

There are known a zoom lens system as disclosed in U.S. Pat. No.5,270,857 wherein any lens unit in a zoom lens system comprised of twoor more lens units is displaced in a direction perpendicular to theoptical axis thereof to correct image shake, and a zoom lens system asdisclosed in U.S. Pat. No. 5,040,881 wherein some lenses in a first lensunit fixed during zooming are displaced in a direction perpendicular tothe optical axis thereof to correct image shake.

However, in the prior art as described above, it has been impossible tosecure a back focal length sufficient for a single-lens reflex camera(SLR) and thus, it has been impossible to realize a desired great zoomratio. Therefore, the zoom lens systems as described above areunsuitable as lenses for a compact and high-performance 35 mmphotographic SLR.

SUMMARY OF THE INVENTION

So, it is an object of the present invention to realize a sufficientback focal length and a great zoom ratio and to provide a compact andhigh-performance zoom lens system with image vibration reductionfunction.

To achieve the above object a zoom lens system with vibration reductionfunction according to an embodiment of the present invention is designedto include, in succession from the object side:

a first lens unit having positive refractive power;

a second lens unit movable along a direction across the optical axisthereof and having negative refractive power;

a third lens unit;

a fourth lens unit having positive refractive power;

a fifth lens unit having negative refractive power;

during the focal-length change from the wide angle end to the telephotoend, the spacing between said first lens unit and said second lens unitbeing increased, the spacing between said second lens unit and saidthird lens unit being varied, and the spacing between said fourth lensunit and said fifth lens unit being decreased; and

a vibration reduction device for moving said second lens unit along adirection across said optical axis;

the stabilization of an image on an image plane being accomplished bythe movement of said second lens unit caused by said vibration reductiondevice.

Also, to achieve the above object, a zoom lens system with vibrationreduction function according to another embodiment of the presentinvention is designed to include, in succession from the object side:

a first lens unit having positive refractive power;

a second lens unit movable along a direction across the optical axisthereof and having negative refractive power;

a lens unit disposed subsequently to said second lens unit; and

a vibration reduction device for moving said second lens unit so as tocross said optical axis;

during the focal-length change from the wide angle end to the telephotoend, the spacing between said first lens unit and said second lens unitbeing increased.

Also, to achieve the above object, a zoom lens system with vibrationreduction function according to still another embodiment of the presentinvention is designed to include, in succession from the object side:

a first lens unit having positive refractive power;

a second lens unit movable along a direction across the optical axisthereof to stabilize an image on an image plane and having negativerefractive power;

a third lens unit;

a fourth lens unit having positive refractive power; and

a fifth lens unit having negative refractive power;

during the focal-length change from the wide angle end to the telephotoend, the spacing between said first lens unit and said second lens unitbeing increased, the spacing between said second lens unit and saidthird lens unit being varied and the spacing between said fourth lensunit and said fifth lens unit being decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the construction of a zoom lens system according to a firstembodiment of the present invention.

FIG. 2 shows the construction of a zoom lens system according to asecond embodiment of the present invention.

FIG. 3 shows the construction of a zoom lens system according to a thirdembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, so as to be suitable particularly for a 35 mmphotographic telephoto zoom lens, is directed to a zoom lens provided,in succession from the object side, with at least a first lens unit G1having positive refractive power and a second lens unit G2 havingnegative refractive power. More specifically, the present inventionbasically adopts a zoom lens of five-unit construction provided, insuccession from the object side, with a first lens unit G1 havingpositive refractive power, a second lens unit G2 having negativerefractive power, a third lens unit G3 having positive or negativerefractive power, a fourth lens unit G4 having positive refractivepower, and a fifth lens unit G5 having negative refractive power.

With attention paid to the features and advantages of a zoom lens ofsuch a five-unit construction type, the action thereof will hereinafterbe described.

By sufficiently making the most of the features of a multi-unitconstruction called the five-unit construction, it is possible torealize a telephoto zoom lens which is compact and excellent in imagingperformance and which can be applied for a higher magnification.

The zoom lens of five-unit construction as described above has the meritthat the full length thereof can be shortened, and particularly at thewide angle end, the full length can be shortened. Also, multi-unitconstruction ensures a great degree of freedom of the manner of movement(movement locus) of the lens units and a great degree of freedom ofaberration correction and therefore, an excellent imaging performancecan be secured even though the zoom ratio is great.

Particularly, in a zoom lens of a type in which, as in the zoom lens ofthe present invention, the full length is short at the wide angle endand the full length stretches during the focal-length change by thezooming from the wide angle end to the telephoto end, the full length atthe wide angle end and the weight of the whole zoom lens can be reduced,as compared with the prior-art telephoto zoom lens of the four-unitafocal type. Also, the heights of rays of light passing through therespective lens units at the wide angle end become small and therefore,aberrations occurring in the respective lens units become small, andthis is particularly advantageous during the aberration correction atthe wide angle side. Further, since the number of the constituent lensunits is great, the degree of freedom of the selection of refractivepower distribution increases and a back focal length sufficient forsingle lens reflex can be secured easily.

Generally, it is often the case with telephoto zoom lenses that thefirst lens unit is comprised of the largest lens unit and is axiallymoved toward the object side during focusing. Therefore, displacing thefirst lens unit in a direction orthogonal to the optical axis thereof tothereby provide a correcting optical system for vibration reductionresults in the bulkiness of a holding mechanism and a driving mechanism,and this is not preferable. Again in the zoom lens of the presentinvention, it is not preferable to use the first lens unit as acorrecting optical system for vibration reduction.

Also, if a lens unit like the third lens unit or the fifth lens unitwhich is greatly moved along the optical axis during focal-length changeis used as a correcting optical system for vibration reduction, themechanism of the lens unit will become complicated, and this is notpreferable.

So, in the zoom lens of the present invention, for the simplification ofthe mechanism of the whole lens system, displacement means 1 foreffecting vibration reduction is provided in the second lens unit. It ispreferable that the second lens unit be fixed during zooming.

Also, in order to intercept unnecessary rays of light incident when thesecond lens unit is displaced across the optical axis for the purpose ofvibration reduction, it is preferable to provide a fixed flare stop onthe optical axis discretely from an aperture stop.

Further, in the above-described construction of the present invention,it is preferable that the following conditional expressions (1) to (3)be satisfied:

    0.3<f1/(fW·fT).sup.1/2 <1.5                       (1)

    0.3<|f2|/f1<5                            (2)

    0.3<|f2|/fW<3                            (3)

where

f1: the focal length of the first lens unit G1;

f2: the focal length of the second lens unit G2;

fW: the focal length of the whole zoom lens system at the wide angleend;

fT: the focal length of the whole zoom lens system at the telephoto end.

Conditional expression (1) prescribes an appropriate range regarding thefocal length fW of the zoom lens at the wide angle end, the focal lengthfT of the zoom lens at the telephoto end, and the focal length f1 of thefirst lens unit G1.

If the upper limit value of conditional expression (1) is exceeded, thefull length at the telephoto end will become great and it will becomeimpossible to realize a compact zoom lens and also, the deficiency ofthe quantity of marginal light at the telephoto end and especially anincrease in the lens diameter of the first lens unit G1 will result, andthis is not preferable. To realize a more compact zoom lens, it ispreferable that the upper limit value be 1.3 or less.

If conversely, the lower limit value of conditional expression (1) isexceeded, the focal length f1 of the first lens unit G1 will become toosmall and the spherical aberration at the telephoto end will tend to beunder-corrected and the fluctuation of curvature of image field duringthe focal-length change by zooming will increase remarkably. Also, themagnitude of the imaging magnification at the telephoto end by thesecond lens unit G2 and subsequent lens units will become excessivelygreat and on-axis chromatic aberration created in the first lens unit G1will be enlarged, and it will become impossible to secure a good imagingperformance. To secure a better imaging performance, it is preferablethat the lower limit value be 0.6 or greater.

Conditional expression (2) is a condition which prescribes anappropriate rate of refractive power on the basis of the focal length f1of the first lens unit G1 and the focal length f2 of the second lensunit G2.

If the upper limit value of conditional expression (2) is exceeded, thespherical aberration at the telephoto end will be liable to becomeexcessively great to the positive side and the fluctuation of comaduring focal-length change will become great, and the distortion at thetelephoto side will greatly move toward the negative side. Also, at thewide angle end, introversive coma will be created in the rays of lightunder the principal ray of light and a good imaging performance couldnot be obtained. If the upper limit value is 2 or less, it will becomepossible to secure a better imaging performance.

If conversely, the lower limit value of conditional expression (2) isexceeded, the spherical aberration at the telephoto end will be liableto become excessively great and the fluctuation of coma duringfocal-length change will become great, and the distortion at thetelephoto side will greatly move toward the positive side. Also, at thewide angle end, introversive coma will be created in the rays of lightunder the principal ray of light and a good imaging performance will notbe obtained. If the lower limit value is 0.5 or greater, it will bepossible to secure a better imaging performance.

Conditional expression (3) prescribes an appropriate rate of themagnitude of the focal length f2 of the second lens unit G2 to the focallength fW of the whole zoom lens system at the wide angle end.

If the upper limit value of conditional expression (3) is exceeded, thefocal length f2 of the second lens unit G2 will become too great.Accordingly, it will become difficult to secure the back focal length atthe wide angle end when for the sake of convenience to explain themeaning of this conditional expression, it is assumed that the thirdlens unit G3 and subsequent lens units maintain a predetermined state.Also, the fluctuation of curvature of image field and the fluctuation ofcoma during the focal-length change by zooming will become too great,and this is inconvenient. Further, if the refractive power of the secondlens unit G2 for effecting vibration reduction is too small (the focallength of this lens unit is too great), the desired amount ofdisplacement (orthogonal to the optical axis) for displaying apredetermined vibration reduction performance will become too great witha result that the mechanism will become bulky or complicated, and thisis inconvenient.

If conversely, the lower limit value of conditional expression (3) isexceeded, the focal length f2 of the second lens unit G2 will become toosmall. Accordingly, when for the sake of convenience to explain themeaning of this conditional expression, it is assumed that the thirdlens unit G3 and subsequent lens units maintain a predetermined state,the full length at the wide angle end will become great and the lensdiameter of the fifth lens unit G5 will become large, and this isinconvenient. Also, if the refractive power of the second lens unit G2which is the correcting lens unit for vibration reduction is too great(the focal length of this lens unit is too small), the desired amount ofdisplacement (orthogonal to the optical axis) for displaying apredetermined vibration reduction performance will become too small witha result that the control of the desired amount of displacement willbecome difficult, and this is inconvenient.

To secure a better performance, it is preferable that in addition toconditional expressions (1) to (3), the following conditionalexpressions (4) and (5) be satisfied:

    ΔS/|f2 |<0.1                       (4)

    0.2<R21/f2<20                                              (5)

where

f2 : the focal length of the second lens unit G2;

ΔS: the magnitude of the maximum amount of displacement during thevibration reduction of the second lens unit G2;

R21: the radius of curvature of that surface of the second lens unit G2which is most adjacent to the object side.

Conditional expression (4) prescribes the appropriate range of the ratioof the magnitude ΔS of the maximum amount of displacement (orthogonal tothe optical axis) during the vibration reduction of the second lens unitG2 to the magnitude of the focal length f2 of the second lens unit G2.

If the upper limit value of conditional expression (4) is exceeded, themaximum amount of displacement of the second lens unit G2 will becometoo great with a result that the fluctuation of aberrations duringvibration reduction will also become great, and this is inconvenient.Particularly, the difference in the direction of the optical axisbetween the best image plane in the meridional direction at the marginalposition on the image plane and the best image plane in the sagittaldirection will widen, and this is inconvenient.

If the upper limit value of conditional expression (5) is exceeded, thespherical aberration at the telephoto end will become excessively greatto the positive side, and at the wide angle end, introversive coma willbe created in the rays of light under the principal ray of light, andthis is inconvenient. It will also be impossible to obtain a goodimaging performance during vibration reduction. If conversely, the lowerlimit of conditional expression (5) is exceeded, the distortion at thetelephoto end will be liable to become excessively great to the positiveside, and at the wide angle end, extroversive coma will be created inthe rays of light under the principal ray of light, and this isinconvenient. It will also be impossible to obtain a good imagingperformance during vibration reduction.

When the second lens unit G2 is actually designed, it is preferable thatin addition to the aforementioned conditions, the following conditionalexpressions (6) and (7) be satisfied:

    1.52<N.sub.-                                               (6)

    0.1<f2-/f2                                                 (7)

where

N-: the refractive index of the concave lens in the second lens unit G2which is most adjacent to the object side;

f2 -: the focal length of the concave lens in the second lens unit G2which is most adjacent to the object side.

If the lower limit value of conditional expression (6) is exceeded, thedistortion at the telephoto end will be liable to become excessivelygreat to the positive side and the fluctuations of various aberrationsduring focal-length change, especially the fluctuation of distortion,will become great, and this is inconvenient. Also, Petzval sum willbecome liable to shift to the positive side, and this is inconvenient.

On the other hand, if the upper limit value of conditional expression(7) is exceeded, the spherical aberration at the telephoto end will beliable to become excessively great to the negative side, and at the wideangle end, extroversive coma will be created in the rays of light underthe principal ray of light, and this is inconvenient. It will also beimpossible to obtain a good imaging performance during vibrationreduction.

If conversely, the lower limit value of conditional expression (7) isexceeded, the distortion at the telephoto end will be liable to becomeexcessively great to the negative side, and at the wide angle end,introversive coma will be created in the rays of light under theprincipal ray of light, and this is inconvenient. Further, thefluctuation of curvature of image field during focal-length change willbecome great, and this is inconvenient. It will also be impossible toobtain a good imaging performance during vibration reduction.

More specifically, it is preferable that the second lens unit G2comprise a cemented lens consisting, in succession from the object side,of a concave lens and a convex lens, and it is preferable that inaddition to the aforementioned conditions, the following conditionalexpressions (8) to (10) be satisfied:

    N.sub.+ <1.55                                              (8)

    -2<q<0                                                     (9)

    Z/T<4                                                      (10)

where

N+: the refractive index of the convex lens;

q: the shape factor of the cemented lens;

T: the magnitude of the amount of movement of the second lens unit G2during vibration reduction;

Z: the magnitude of the amount of movement of the image corresponding tothe amount of movement of the second lens unit G2.

When the radius of curvature of the object side lens surface of thecemented lens is ra and the radius of curvature of the image side lenssurface of the cemented lens is rb, the shape factor q is expressed by

    q=(rb+ra)/(rb-ra).

Conditional expression (10) prescribes the appropriate ratio of themagnitude of the amount of movement of the second lens unit G2 to themagnitude of the corresponding amount of movement of the image so thatthe control of the minute amount of displacement of the image may becomepossible. To obtain a better imaging performance, it is preferable thatthe upper limit value of conditional expression (10) be 2.

Further, it is preferable that in addition to the aforementionedconditions, the following conditional expression (11) be satisfied:

    0.5<f4/|f5|<2                            (11)

where

f4: the focal length of the fourth lens unit G4;

f5: the focal length of the fifth lens unit G5.

If the upper limit value of conditional expression (11) is exceeded, theastigmatism at the wide angle end will become great, and at the wideangle end and the telephoto end, distortion will greatly move toward thepositive side and Petzval sum will become liable to shift to thenegative side, and this is inconvenient.

If the lower limit value of conditional expression (11) is exceeded, atthe wide angle end and the telephoto end, distortion will become verygreat to the negative side and coma will also be created greatly, andthis is inconvenient.

The third lens unit G3 can obtain a good performance if it is a lensunit having positive refractive power or a lens unit having negativerefractive power. However, to secure a better imaging performance, it ispreferable when the third lens unit G3 has positive refractive powerthat the following conditional expression (12) be satisfied:

    0.6<f3/fW<2                                                (12)

where

f3: the focal length of the third lens unit G3;

fW: the focal length of the whole zoom lens system at the wide angleend.

If the upper limit value of conditional expression (12) is exceeded,spherical aberration will become very great to the positive side at thetelephoto end and the lens diameters of the fourth lens unit G4 andsubsequent lens unit will become large, and this is inconvenient. Also,Petzval sum will become liable to shift to the negative side, and thisis inconvenient.

If conversely, the lower limit value of conditional expression (12) isexceeded, at the telephoto end, spherical aberration will become verygreat to the negative side and coma will be created, and this isinconvenient. Also, the back focal length at the wide angle end will beliable to become short, and this is inconvenient.

On the other hand, where the third lens unit G3 has negative refractivepower, it is preferable in order to secure a better imaging performancethat the following conditional expression (13) be satisfied:

    1<|f3|/fW<2.5                            (13)

If the upper limit value of conditional expression (13) is exceeded, theback focal length at the wide angle end will be liable to become shortand the fluctuation of curvature of image field and the fluctuation ofcoma will become great during focal-length change, and this isinconvenient.

If conversely, the lower limit value of conditional expression (13) isexceeded, spherical aberration will become very great to the positiveside at the telephoto end and the lens diameter of the fourth lens unitG4 and subsequent lens unit will become large, and this is inconvenient.

A zoom lens system according to each embodiment of the present inventionwill hereinafter be described with reference to the drawings. The zoomlens system according to each embodiment has, in succession from theobject side, a first lens unit G1 having positive refractive power, asecond lens unit G2 having negative refractive power, a third lens unitG3 having positive or negative refractive power a fourth lens unit G4having positive refractive power, and a fifth lens unit G5 havingnegative refractive power.

The zoom lens system according to each embodiment is designed such thatduring the focal-length change from the wide angle end to the telephotoend, the spacing between the first lens unit G1 and the second lens unitG2 is increased, the spacing between the second lens unit G2 and thethird lens unit G3 is linearly or non-linearly varied and the spacingbetween the fourth lens unit G4 and the fifth lens unit G5 is decreased.

Further, in the zoom lens system according to each embodiment, thesecond lens unit G2 is designed to be movable along a directionsubstantially orthogonal to the optical axis thereof. Each embodiment isprovided with a vibration reduction device 1 for moving the second lensunit G2. This vibration reduction device 1 may be, for example, onedisclosed in commonly owned U.S. patent application Ser. No. 129,580(filed on Sep. 30, 1993) now abandoned or U.S. patent application Ser.No. 131,939 (filed on Oct. 5, 1993,) now abandoned.

Each embodiment of the present invention will hereinafter be describedwith reference to the drawings.

[Embodiment 1]

FIG. 1 shows the construction of a zoom lens according to a firstembodiment of the present invention. The zoom lens shown in FIG. 1 iscomprised, in succession from the object side, a first lens unit G1comprising a cemented lens consisting of a negative meniscus lens havingits convex surface facing the object side and a biconvex lens, and abiconvex lens, a second lens unit G2 comprising a cemented lensconsisting of a biconcave lens and a positive meniscus lens having itsconvex surface facing the object side, a third lens unit G3 comprising acemented lens consisting of a biconcave lens and a biconvex lens, afourth lens unit G4 comprising a cemented lens consisting of a biconvexlens and a negative meniscus lens having its concave surface facing theobject side, and a cemented lens consisting of a biconvex lens and anegative meniscus lens having its concave surface facing the objectside, and a fifth lens unit G5 comprising a cemented lens consisting ofa biconvex lens and a biconcave lens. An aperture stop S is providedbetween the third lens unit G3 and the fourth lens unit G4.

FIG. 1 shows the positional relations among the lens units at the wideangle end, and during the focal-length change to the telephoto end, thelens units are moved on the optical axis along zooming loci indicated byarrows. However, the second lens unit G2 is fixed during zooming, and issuitably moved in a direction substantially orthogonal to the opticalaxis by the vibration reduction device 1 which is displacing means sothat the shake of an image attributable to the vibration of the zoomlens may be corrected.

The values of the numerical data of Embodiment 1 of the presentinvention are given in Table 1 below. In Table 1, f represents the focallength, F_(NO) represents the F-number, 2ω represents the angle offield, and Bf represents the back focal length. Further, the numbers atthe left end indicate the order of the lens surfaces from the objectside, r indicates the radius of curvature of each lens surface, dindicates the spacing between adjacent lens surfaces, and n indicatesthe refractive index.

                  TABLE 1                                                         ______________________________________                                        f = 76.5 ˜ 150                                                          F.sub.NO = 4.62 ˜ 5.63                                                  2ω = 32.56 ˜ 15.96                                                      r             d            n                                            ______________________________________                                        1     280.061       2.000        1.79631                                      2     77.586        7.300        1.49782                                      3     -428.027      0.200                                                     4     87.627        6.500        1.51860                                      5     -427.962      (d5 = variable)                                           6     -142.978      1.700        1.54814                                      7     22.745        5.500        1.62000                                      8     104.648       (d8 = variable)                                           9     -52.404       1.500        1.78797                                      10    56.961        3.600        1.64831                                      11    -75.627       (d11 = variable)                                          12    152.933       3.000        1.71700                                      13    -43.246       1.600        1.86074                                      14    -83.642       0.500                                                     15    71.466        4.500        1.62280                                      16    -42.561       1.600        1.80384                                      17    -150.924      (d17 = variable)                                          18    156.427       3.700        1.80384                                      19    -36.315       1.500        1.77279                                      20    33.124        (Bf)                                                      ______________________________________                                        (Variable spacings in focal-length change)                                    f                   76.500  150.000                                           DO                  ∞ ∞                                           d5                   2.053  25.928                                            d8                   4.134  20.131                                            d11                 55.356  23.734                                            d17                 30.166  21.916                                            Bf                  41.518  65.393                                            ______________________________________                                        (Condition-corresponding values)                                              f1 = 137.3                                                                    f2 = -151                                                                     fW = 76.5                                                                     fT = 150                                                                      R21 = -142.978                                                                f2.sub.--  = -35.671                                                          (1)          f1/(fW · fT).sup.1/2                                                                = 1.282                                           (2)          |f2|/f1                                                                    = 1.0998                                          (3)          |f2|/fW                                                                    = 1.974                                           (4)          ΔS/|f2|                                                              = 0.003565                                        (5)          R21/f2         = 0.94687                                         (6)          N.sub.--       = 1.54814                                         (7)          f2.sub.-- /f2  = 0.2362                                          (8)          N+             = 1.62004                                         (9)          q              = -0.7255                                         (11)         f4/|f5|                                                                    = 0.807                                           (13)         |f3|/fW                                                                    = 1.536                                           ______________________________________                                        (Vibration reduction data)                                                    Amount of movement of second                                                                      Wide angle                                                                              Telephoto                                       lens unit in direction                                                                            end       end                                             ______________________________________                                        Orthogonal to optical axis (mm)                                                                   0.5383    0.478                                           Amount of movement of image (mm)                                                                  -0.255    -0.35                                           ______________________________________                                    

[Embodiment 2]

FIG. 2 shows the construction of a zoom lens according to a secondembodiment of the present invention. The zoom lens shown in FIG. 2 iscomprised, in succession from the object side, of a first lens unit G1comprising a cemented lens consisting of a negative meniscus lens havingits convex surface facing the object side and a biconvex lens, and abiconvex lens, a second lens unit G2 comprising a cemented lensconsisting of a biconcave lens and a positive meniscus lens having itsconvex surface facing the object side, a third lens unit G3 comprising acemented lens consisting of a negative meniscus lens having its concavesurface facing the object side and a negative meniscus lens having itsconcave surface facing the object side, a fourth lens unit G4 comprisinga positive meniscus lens having its convex surface facing the objectside, a biconvex lens and a cemented lens consisting of a biconvex lensand a negative meniscus lens having its concave surface facing theobject side, and a fifth lens unit G5 comprising a cemented lensconsisting of a biconvex lens and a biconcave lens. An aperture stop Sis provided between the third lens unit G3 and the fourth lens unit G4.

FIG. 2 shows the positional relations among the lens units at the wideangle end, and during the focal-length change to the telephoto end, thelens units are suitably moved on the optical axis along zooming loci.However, the second lens unit G2 is fixed during zooming, and issuitably moved in a direction substantially orthogonal to the opticalaxis by the vibration reduction device 1 so that the shake of an imageattributable to the vibration of the zoom lens may be corrected.

The zoom lens of Embodiment 2 is similar in basic construction to thezoom lens of Embodiment 1, but differs from the zoom lens of Embodiment1 in the refractive power, shape, etc. of each lens unit.

The values of the numerical data of Embodiment 2 of the presentinvention are given in Table 2 below. In Table 2, f represents the focallength, F_(NO) represents the F-number, 2ω represents the angle offield, and Bf represents the back focal length. Further, the numbers atthe left end indicate the order of the lens surfaces from the objectside, r indicates the radius of curvature of each lens surface, dindicates the spacing between adjacent lens surfaces, and n indicatesthe refractive index.

                  TABLE 2                                                         ______________________________________                                        f = 100 ˜ 292                                                           F.sub.NO = 4.62 ˜ 5.69                                                  2ω = 23.32° ˜ 8.18°                                       r             d            n                                            ______________________________________                                        1     244.826       2.000        1.80218                                      2     60.389        7.500        1.49782                                      3     -477.858      0.200                                                     4     64.724        7.200        1.51860                                      5     -515.076      (d5 = variable)                                           6     -1586.105     2.000        1.75692                                      7     23.033        3.600        1.80458                                      8     105.850       (d8 = variable)                                           9     -39.172       2.000        1.77279                                      10    -112.696      2.300        1.80458                                      11    -58.945       (d11 = variable)                                          12    55.101        2.500        1.86074                                      13    31.581        3.000                                                     14    386.036       4.000        1.51860                                      15    -104.239      0.500                                                     16    37.534        4.000        1.56384                                      17    -33.568       1.500        1.67270                                      18    -51.350       (d18 = variable)                                          19    121.195       2.500        1.80458                                      20    -39.387       1.800        1.80411                                      21    34.827        (Bf)                                                      ______________________________________                                        (Variable spacings in focal-length change)                                    f                   100.00  292.00                                            DO                  ∞ ∞                                           d5                  7.866   58.597                                            d8                  9.124   12.282                                            d11                 30.506  5.712                                             d18                 29.499  0.406                                             Bf                  38.720  89.452                                            ______________________________________                                        (Condition-corresponding values)                                              f1 = 120                                                                      f2 = -167                                                                     fW = 100                                                                      fT = 292                                                                      R21 = -1586.105                                                               f2.sub.--  = -29.979                                                          (1)          f1/(fW · fT).sup.1/2                                                                = 0.69363                                         (2)          |f2|/f1                                                                    = 1.3917                                          (3)          |f2|/fW                                                                    = 1.629293                                        (4)          ΔS/|f2|                                                              = 0.005161                                        (5)          R21/f2         = 9.498                                           (6)          N.sub.--       = 1.75692                                         (7)          f2.sub.-- /f2  = 0.17952                                         (8)          N+             = 1.80458                                         (9)          q              = -0.97137                                        (11)         f4/|f5|                                                                    = 1.06834                                         (13)         |f3|/fW                                                                    = 1.716                                           ______________________________________                                        (Vibration reduction data)                                                    Amount of movement of second                                                                      Wide angle                                                                              Telephoto                                       lens unit in direction                                                                            end       end                                             ______________________________________                                        Orthogonal to optical axis (mm)                                                                   0.47472   0.86183                                         Amount of movement of image (mm)                                                                  -0.255    -0.68136                                        ______________________________________                                    

[Embodiment 3]

FIG. 3 shows the construction of a zoom lens according to a thirdembodiment of the present invention. The zoom lens shown in FIG. 3 arecomprised, in succession from the object side, of a first lens unit G1comprising a negative meniscus lens having its convex surface facing theobject side and a biconvex lens, a second lens unit G2 comprising acemented lens consisting of a biconcave lens and a biconvex lens, athird lens unit G3 comprising a cemented lens consisting of a biconcavelens and a biconvex lens, a fourth lens unit G4 comprising a cementedlens consisting of a biconvex lens and a negative meniscus lens havingits concave surface facing the object side, and a fifth lens unit G5comprising a positive meniscus lens having its concave surface facingthe object side and a biconcave lens. An aperture stop S is providedbetween the second lens unit G2 and the third lens unit G3.

FIG. 3 shows the positional relations among the lens units at the wideangle end, and during the focal-length change to the telephoto end, thelens units are moved on the optical axis along zooming loci indicated byarrows. However, the second lens unit G2 and the fourth lens unit G4 arefixed during zooming, and the second lens unit G2 is suitably moved in adirection substantially orthogonal to the optical axis by the vibrationreduction device 1 so that the shake of an image attributable to thevibration of the zoom lens may be corrected.

The zoom lens of Embodiment 3 is similar in basic construction to thezoom lens of Embodiment 1 , but differs from the zoom lens of Embodiment1 in the refractive power, shape, etc. of each lens unit.

The values of the numerical data of Embodiment 3 of the presentinvention are given in Table 3 below. In Table 3, f represents the focallength, F_(NO) represents the F-number, 2ω represents the angle offield, and Bf represents the back focal length. Further, the numbers atthe left end indicate the order of the lens surfaces from the objectside, r indicates the radius of curvature of each lens surface, dindicates the spacing between adjacent lens surfaces, and n indicatesthe refractive index.

                  TABLE 3                                                         ______________________________________                                        f = 83.2 ˜ 166                                                          F.sub.NO = 4.62 ˜ 5.84                                                  2ω = 28.92° ˜ 14.28°                                      r             d            n                                            ______________________________________                                        1     52.733        1.800        1.79504                                      2     38.910        0.430                                                     3     41.785        5.300        1.59319                                      4     -430.357      (d4 = variable)                                           5     -48.679       1.100        1.84042                                      6     35.750        3.000        1.80518                                      7     -1346.158     (d7 = variable)                                           8     -166.474      1.100        1.84666                                      9     73.573        5.500        1.60311                                      10    -32.325       (d10 = variable)                                          11    32.688        5.800        1.53172                                      12    -34.756       1.000        1.83400                                      13    -104.388      (d13 = variable)                                          14    -128.191      2.800        1.80518                                      15    -30.240       1.100                                                     16    -28.083       1.200        1.77279                                      17    39.596        (Bf)                                                      ______________________________________                                        (Variable spacings in focal-length change)                                    f                   83.196  166.00                                            DO                  ∞ ∞                                           d4                   1.960  35.092                                            d7                  25.240  10.840                                            d10                  0.336  14.727                                            d13                 20.313  5.922                                             Bf                  40.139  54.530                                            ______________________________________                                        (Condition-corresponding values)                                              f1 = 97.233                                                                   f2 = -56.696                                                                  fW = 83.196                                                                   fT = 166                                                                      R21 = -48.680                                                                 f2.sub.--  = -24.3812                                                         (1)          f1/(fW · fT).sup.1/2                                                                = 1.209                                           (2)          |f2|/f1                                                                    = 0.583                                           (3)          |f2|/fW                                                                    = 0.6815                                          (4)          ΔS/|f2|                                                              = 0.002998                                        (5)          R21/f2         = 0.859                                           (6)          N.sub.--       = 1.84042                                         (7)          f2.sub.-- /f2  = 0.43003                                         (8)          N+             = 1.80518                                         (9)          q              = -0.1531                                         (11)         f4/|f5|                                                                    = 1.6643                                          (12)         f3/fW          = 1.108                                           (Vibration reduction data)                                                    Amount of movement of second                                                                      Wide angle                                                                              Telephoto                                       lens unit in direction                                                                            end       end                                             ______________________________________                                        Orthogonal to optical axis (mm)                                                                   0.15      0.17                                            Amount of movement of image (mm)                                                                  -0.206    -0.297                                          ______________________________________                                    

While in the present embodiment, the invention has been described withrespect to a zoom lens of five-unit construction provided, in successionfrom the object side, with a first lens unit having positive refractivepower, a second lens unit having negative refractive power, a third lensunit having positive or negative refractive power, a fourth lens unithaving positive refractive power, and a fifth lens unit having negativerefractive power, it is apparent that the present invention can also beapplied to an ordinary zoom lens comprising a plurality of lens unitsprovided, in succession from the object side, with a first lens unithaving positive refractive power, and a second lens unit having negativerefractive power.

Also, while in the present embodiment, the entire second lens unit ismoved in the direction orthogonal to the optical axis by the vibrationreduction device which is displacing means, it is apparent that theoperational effect of the present invention is also achieved by movingonly some lens groups or lenses in the second lens unit.

What is claimed is:
 1. A zoom lens system with vibration reductionfunction including, in succession from an object side:a first lens unithaving positive refractive power; a second lens unit movable along adirection across an optical axis thereof and having negative refractivepower; a third lens unit; a fourth lens unit having positive refractivepower; a fifth lens unit having negative refractive power; during afocal-length change from the wide angle end to the telephoto end,spacing between said first lens unit and said second lens unit beingincreased, spacing between said second lens unit and said third lensunit being varied, and spacing between said fourth lens unit and saidfifth lens unit being decreased; a vibration reduction device for movingsaid second lens unit in the direction across said optical axis; thestabilization of an image on an image plane being accomplished by themovement of said second lens unit caused by said vibration reductiondevice; and wherein the following condition is satisfied: 0.3<f1/(fW·fT)^(1/2) <1.5, wheref1: the focal length of said first lensunit; fW: the focal length of the whole zoom lens system at said wideangle end; fT: the focal length of the whole zoom lens system at saidtelephoto end, and wherein said second lens unit includes a cementedlens component having, in succession from the object side, a concavelens element and a convex lens element, and satisfies the followingcondition:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 2. A zoomlens system with vibration reduction function according to claim 1,satisfying the following condition:

    0.3<|f2|/f1<5,

where is the focal length of said second lens unit.
 3. A zoom lenssystem with vibration reduction function according to claim 1,satisfying the following condition:

    0.3<|f2|/fW<3,

where f2: the focal length of said second lens unit.
 4. A zoom lenssystem with vibration reduction function according to claim 1,satisfying the following conditions:

    ΔS/|f2|<0.1,

where f2: the focal length of said second lens unit; ΔS: a maximumamount of displacement which can be assumed by said second lens unit forthe stabilization of said image.
 5. A zoom lens system with vibrationreduction function according to claim 1, satisfying the followingcondition:

    0.2<R21/f2<20,

where f2: the focal length of said second lens unit; R21: the radius ofcurvature of that lens surface in said second lens unit which ispositioned most adjacent to the object side.
 6. A zoom lens system withvibration reduction function according to claim 1, satisfying thefollowing condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 7. A zoom lens system with vibration reduction function accordingto claim 1, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 8. A zoomlens system with vibration reduction function according to claim 1,wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element, and f2 isthe focal length of said second lens unit.
 9. A zoom lens system withvibration reduction function according to claim 1, wherein said secondlens unit is fixed during the focal-length change from the wide angleend to the telephoto end.
 10. A zoom lens system with vibrationreduction function according to claim 1, satisfying the followingcondition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 11. A zoom lenssystem with vibration reduction function according to claim 1, having aflare stop disposed on the image side of said second lens unit, saidflare stop being fixed with respect to the direction across the opticalaxis.
 12. A zoom lens system with vibration reduction functionincluding, in succession from an object side:a first lens unit havingpositive refractive power; a second lens unit movable along a directionacross an optical axis thereof and having negative refractive power; athird lens unit; a fourth lens unit having positive refractive power; afifth lens unit having negative refractive power; during a focal-lengthchange from the wide angle end to the telephoto end, spacing betweensaid first lens unit and said second lens unit being increased, spacingbetween said second lens unit and said third lens unit being varied, andspacing between said fourth lens unit and said fifth lens unit beingdecreased; a vibration reduction device for moving said second lens unitin the direction across said optical axis; the stabilization of an imageon an image plane being accomplished by the movement of said second lensunit caused by said vibration reduction device; and wherein thefollowing condition is satisfied:
 0. 3<|f2|/f1<5, where f1 is the focallength of said first lens unit, and f2 is the focal length of saidsecond lens unit, and wherein said second lens unit includes a cementedlens component having, in succession from the object side, a concavelens element and a convex lens element, and satisfies the followingcondition:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 13. A zoomlens system with vibration reduction function according to claim 12satisfying the following condition:

    0.3<|f2|/fW<3,

where fW: the focal length of the whole zoom lens system at said wideangle end.
 14. A zoom lens system with vibration reduction functionaccording to claim 12, satisfying the following condition:

    ΔS|f2|<0.1,

where ΔS: a maximum amount of displacement which can be assumed by saidsecond lens unit for the stabilization of said image.
 15. A zoom lenssystem with vibration reduction function according to claim 12,satisfying the following condition:

    0.2<R21/f2<20,

where R21: the radius of curvature of that lens surface in said secondlens unit which is positioned most adjacent to the object side.
 16. Azoom lens system with vibration reduction function according to claim12, satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 17. A zoom lens system with vibration reduction function accordingto claim 12, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 18. Azoom lens system with vibration reduction function according to claim12, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element.
 19. A zoomlens system with vibration reduction function according to claim 12,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 20. A zoom lens systemwith vibration reduction function according to claim 12, satisfying thefollowing condition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 21. A zoom lenssystem with vibration reduction function according to claim 12, having aflare stop disposed on the image side of said second lens unit saidflare stop being fixed with respect to the direction across the opticalaxis.
 22. A zoom lens system with vibration reduction functionincluding, in succession from an object side:a first lens unit havingpositive refractive power; a second lens unit movable along a directionacross an optical axis thereof and having negative refractive power; athird lens unit; a fourth lens unit having positive refractive power; afifth lens unit having negative refractive power; during a focal-lengthchange from the wide angle end to the telephoto end, spacing betweensaid first lens unit and said second lens unit being increased, spacingbetween said second lens unit and said third lens unit being varied, andspacing between said fourth lens unit and said fifth lens unit beingdecreased; a vibration reduction device for moving said second lens unitin the direction across said optical axis; the stabilization of an imageon an image plane being accomplished by the movement of said second lensunit caused by said vibration reduction device; and wherein thefollowing condition is satisfied:

    ΔS/|f2|<0.1,

wheref2: the focal length of said second lens unit; ΔS: a maximum amountof displacement which can be assumed by said second lens unit for thestabilization of said image, and wherein said second lens unit includesa cemented lens component having, in succession from the object side, aconcave lens element and a convex lens element, and satisfies thefollowing condition:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 23. A zoomlens system with vibration reduction function according to claim 22,satisfying the following condition:

    0.2<R21/f2<20,

where R21: the radius of curvature of that lens surface in said secondlens unit which is positioned most adjacent to the object side.
 24. Azoom lens system with vibration reduction function according to claim22, satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 25. A zoom lens system with vibration reduction function accordingto claim 22, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 26. Azoom lens system with vibration reduction function according to claim22, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2 - is the focal length of said concave lens element.
 27. A zoomlens system with vibration reduction function according to claim 22,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 28. A zoom lens systemwith vibration reduction function according to claim 22, satisfying thefollowing condition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 29. A zoom lenssystem with vibration reduction function according to claim 22, having aflare stop disposed on the image side of said second lens unit, saidflare stop being fixed with respect to the direction across the opticalaxis.
 30. A zoom lens system with vibration reduction functionincluding, in succession from an object side:a second lens unit movablealong a direction across an optical axis thereof and having negativerefractive power; a third lens unit; a fourth lens unit having positiverefractive power; a fifth lens unit having negative refractive power;during a focal-length change from the wide angle end to the telephotoend, spacing between said first lens unit and said second lens unitbeing increased, spacing between said second lens unit and said thirdlens unit being varied, and spacing between said fourth lens unit andsaid fifth lens unit being decreased; a vibration reduction device formoving said second lens unit in the direction across said optical axis;the stabilization of an image on an image plane being accomplished bythe movement of said second lens unit caused by said vibration reductiondevice; and wherein the following condition is satisfied:

    0.2<R21/f2<20,

wheref2: the focal length of said second lens unit; R21: the radius ofcurvature of that lens surface in said second lens unit which ispositioned most adjacent to the object side, and wherein said secondlens unit includes a cemented lens component having, in succession fromthe object side, a concave lens element and a convex lens element, andsatisfies the following condition:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 31. A zoomlens system with vibration reduction function according to claim 30,satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 32. A zoom lens system with vibration reduction function accordingto claim 30, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 33. Azoom lens system with vibration reduction function according to claim30, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element.
 34. A zoomlens system with vibration reduction function according to claim 30,unit is fixed during the focal-length change from the wide angle end tothe telephoto end.
 35. A zoom lens system with vibration reductionfunction according to claim 30, satisfying the following condition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 36. A zoom lenssystem with vibration reduction function according to claim 30, having aflare stop disposed on the image side of said second lens unit, saidflare stop being fixed with respect to the direction across the opticalaxis.
 37. A zoom lens system with vibration reduction functionincluding, in succession from an object side:a first lens unit havingpositive refractive power; a second lens unit movable along a directionacross an optical axis thereof and having negative refractive power; athird lens unit; a fourth lens unit having positive refractive power; afifth lens unit having negative refractive power; during a focal-lengthchange from the wide angle end to the telephoto end, spacing betweensaid first lens unit and said second lens unit being increased, spacingbetween said second lens unit and said third lens unit being varied, andspacing between said fourth lens unit and said fifth lens unit beingdecreased; a vibration reduction device for moving said second lens unitin the direction across said optical axis; the stabilization of an imageon an image plane being accomplished by the movement of said second lensunit caused by said vibration reduction device; and wherein said secondlens unit includes a cemented lens component having, in succession fromthe object side, a concave lens element and a convex lens element, andthe following condition is satisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element, and f2 isthe focal length of said second lens unit, and wherein the followingcondition is satisfied:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 38. A zoomlens system with vibration reduction function according to claim 37,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 39. A zoom lens systemwith vibration reduction function according to claim 37, having a flarestop disposed on the image side of said second lens unit, said flarestop being fixed with respect to the direction across the optical axis.40. A zoom lens system with vibration reduction function including, insuccession from an object side:a first lens unit having positiverefractive power; a second lens unit movable along a direction across anoptical axis thereof and having negative refractive power; a third lensunit; a fourth lens unit having positive refractive power; a fifth lensunit having negative refractive power; during a focal-length change fromthe wide angle end to the telephoto end, spacing between said first lensunit and said second lens unit being increased, spacing between saidsecond lens unit and said third lens unit being varied, and spacingbetween said fourth lens unit and said fifth lens unit being decreased;a vibration reduction device for moving said second lens unit in thedirection across said optical axis; the stabilization of an image on animage plane being accomplished by the movement of said second lens unitcaused by said vibration reduction device; and wherein said second lensunit includes a cemented lens component having, in succession from theobject side, a concave lens element and a convex lens element, andsatisfies the following condition:

    -< q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component, and wherein thefollowing condition is satisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element, and f2 isthe focal length of said second lens unit.
 41. A zoom lens system withvibration reduction function including, in succession from an objectside:a first lens unit having positive refractive power; a second lensunit movable along a direction across an optical axis thereof and havingnegative refractive power; a third lens unit; a fourth lens unit havingpositive refractive power; a fifth lens unit having negative refractivepower; during a focal-length change from the wide angle end to thetelephoto end, spacing between said first lens unit and said second lensunit being increased, spacing between said second lens unit and saidthird lens unit being varied, and spacing between said fourth lens unitand said fifth lens unit being decreased; a vibration reduction devicefor moving said second lens unit in the direction across said opticalaxis; the stabilization of an image on an image plane being accomplishedby the movement of said second lens unit caused by said vibrationreduction device; and wherein said second lens unit includes a cementedlens component having, in succession from the object side, a concavelens element and a convex lens element, and satisfies the followingcondition:

    N+<1.55,

where N+ is the refractive index of said convex lens element.
 42. A zoomlens system with vibration reduction function according to claim 41,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 43. A zoom lens systemwith vibration reduction function according to claim 41, satisfying thefollowing condition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 44. A zoom lenssystem with vibration reduction function including, in succession froman object side:a first lens unit having positive refractive power; asecond lens unit movable along a direction across an optical axisthereof and having negative refractive power; a third lens unit; afourth lens unit having positive refractive power; a fifth lens unithaving negative refractive power; during a focal-length change from thewide angle end to the telephoto end, spacing between said first lensunit and said second lens unit being increased, spacing between saidsecond lens unit and said third lens unit being varied, and spacingbetween said fourth lens unit and said fifth lens unit being decreased;a vibration reduction device for moving said second lens unit in thedirection across said optical axis; the stabilization of an image on animage plane being accomplished by the movement of said second lens unitcaused by said vibration reduction device; and wherein the followingcondition is satisfied:

    0.3<f1/(fW·fT).sup.1/2 <1.5,

wheref1: the focal length of said first lens unit; fW: the focal lengthof the whole zoom lens system at said wide angle end; fT: the focallength of the whole zoom lens system at said telephoto end, and whereinsaid second lens unit includes a cemented lens component having, insuccession from the object side, a concave lens element and a convexlens element, and satisfies the following condition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 45. A zoom lenssystem with vibration reduction function according to claim 44,satisfying the following condition:

    0.3<|f2|/f1<5,

where f2 is the focal length of said second lens unit.
 46. A zoom lenssystem with vibration reduction function according to claim 44,satisfying the following condition:

    0.3<|f2|/fW<3,

where f2 : the focal length of said second lens unit.
 47. A zoom lenssystem with vibration reduction function according to claim 44,satisfying the following condition:

    ΔS/|f2|<0.1,

where f2: the focal length of said second lens unit; ΔS: a maximumamount of displacement which can be assumed by said second lens unit forthe stabilization of said image.
 48. A zoom lens system with vibrationreduction function according to claim 44, satisfying the followingcondition:

    0.2<R21/f2<20,

where f2 : the focal length of said second lens unit; R21: the radius ofcurvature of that lens surface in said second lens unit which ispositioned most adjacent to the object side.
 49. A zoom lens system withvibration reduction function according to claim 44, satisfying thefollowing condition:

    Z/t<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 50. A zoom lens system with vibration reduction function accordingto claim 44, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 51. Azoom lens system with vibration reduction function according to claim44, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element, and f2 isthe focal length of said second lens unit.
 52. A zoom lens system withvibration reduction function according to claim 44, wherein said secondlens unit is fixed during the focal-length change from the wide angleend to the telephoto end.
 53. A zoom lens system with vibrationreduction function according to claim 44, having a flare stop disposedon the image side of said second lens unit, said flare stop being fixedwith respect to the direction across the optical axis.
 54. A zoom lenssystem with vibration reduction function including, in succession froman object side:a first lens unit having positive refractive power; asecond lens unit movable along a direction across an optical axisthereof and having negative refractive power; a third lens unit; afourth lens unit having positive refractive power; a fifth lens unithaving negative refractive power; during a focal-length change from thewide angle end to the telephoto end, spacing between said first lensunit and said second lens unit being increased, spacing between saidsecond lens unit and said third lens unit being varied, and spacingbetween said fourth lens unit and said fifth lens unit being decreased;a vibration reduction device for moving said second lens unit in thedirection across said optical axis; the stabilization of an image on animage plane being accomplished by the movement of said second lens unitcaused by said vibration reduction device; and wherein the followingcondition is satisfied:
 0. 3<|f2|/f1<5, where f1 is the focal length ofsaid first lens unit, and f2 is the focal length of said second lensunit, and wherein said second lens unit includes a cemented lenscomponent having, in succession from the object side, a concave lenselement and a convex lens element, and satisfies the followingcondition:

    -2<q-0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 55. A zoom lenssystem with vibration reduction function according to claim 54,satisfying the following condition:

    0.3<|f2|/fW<3,

where fW: the focal length of the whole zoom lens system at said wideangle end.
 56. A zoom lens system with vibration reduction functionaccording to claim 54, satisfying the following condition:where ΔS: amaximum amount of displacement which can be assumed by said second lensunit for the stabilization of said image.
 57. A zoom lens system withvibration reduction function according to claim 54, satisfying thefollowing condition:

    0.2<R21/f2<20,

where R21: the radius of curvature of that lens surface in said secondlens unit which is positioned most adjacent to the object side.
 58. Azoom lens system with vibration reduction function according to claim54, satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 59. A zoom lens system with vibration reduction function accordingto claim 54, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 60. Azoom lens system with vibration reduction function according to claim54, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element.
 61. A zoomlens system with vibration reduction function according to claim 54,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 62. A zoom lens systemwith vibration reduction function according to claim 54, having a flarestop disposed on the image side of said second lens unit, said flarestop being fixed with respect to the direction across the optical axis.63. A zoom lens system with vibration reduction function including, insuccession from an object side:a first lens unit having positiverefractive power; a second lens unit movable along a direction across anoptical axis thereof and having negative refractive power; a third lensunit; a fourth lens unit having positive refractive power; a fifth lensunit having negative refractive power; during a focal-length change fromthe wide angle end to the telephoto end, spacing between said first lensunit and said second lens unit being increased, spacing between saidsecond lens unit and said third lens unit being varied, and spacingbetween said fourth lens unit and said fifth lens unit being decreased;a vibration reduction device for moving said second lens unit in thedirection across said optical axis; the stabilization of an image on animage plane being accomplished by the movement of said second lens unitcaused by said vibration reduction device; and wherein the followingcondition is satisfied:

    ΔS/|f2<0.1,

wheref2: the focal length of said second lens unit; ΔS: a maximum amountof displacement which can be assumed by said second lens unit for thestabilization of said image, and wherein said second lens unit includesa cemented lens component having, in succession from the object side, aconcave lens element and a convex lens element, and satisfies thefollowing condition:

    -< q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 64. A zoom lenssystem with vibration reduction function according to claim 63,satisfying the following condition:

    0.2<R21/f2<20,

where R21: the radius of curvature of that lens surface in said secondlens unit which is positioned most adjacent to the object side.
 65. Azoom lens system with vibration reduction function according to claim63, satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 66. A zoom lens system with vibration reduction function accordingto claim 63, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 67. Azoom lens system with vibration reduction function according to claim63, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element.
 68. A zoomlens system with vibration reduction function according to claim 63,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 69. A zoom lens systemwith vibration reduction function according to claim 63, having a flarestop disposed on the image side of said second lens unit, said flarestop being fixed with respect to the direction across the optical axis.70. A zoom lens system with vibration reduction function including, insuccession from an object side:a first lens unit having positiverefractive power; a second lens unit movable along a direction across anoptical axis thereof and having negative refractive power; a third lensunit; a fourth lens unit having positive refractive power; a fifth lensunit having negative refractive power; during a focal-length change fromthe wide angle end to the telephoto end, spacing between said first lensunit and said second lens unit being increased, spacing between saidsecond lens unit and said third lens unit being varied, and spacingbetween said fourth lens unit and said fifth lens unit being decreased;a vibration reduction device for moving said second lens unit in thedirection across said optical axis; the stabilization of an image on animage plane being accomplished by the movement of said second lens unitcaused by said vibration reduction device; and wherein the followingcondition is satisfied:
 0. 2<R21/f2<20, wheref2: the focal length ofsaid second lens unit; R21: the radius of curvature of that lens surfacein said second lens unit which is positioned most adjacent to the objectside, and wherein said second lens unit includes a cemented lenscomponent having, in succession from the object side, a concave lenselement and a convex lens element, and satisfies the followingcondition:

    -2<q<0

    q=(rb+ra)/(rb-ra)

where ra is the radius of curvature of the object side lens surface ofsaid cemented lens component, and rb is the radius of curvature of theimage side lens surface of said cemented lens component.
 71. A zoom lenssystem with vibration reduction function according to claim 70,satisfying the following condition:

    Z/T<4,

where T: the amount of movement of said second lens unit when thestabilization of said image is effected; Z: the amount of movement ofthe image corresponding to the amount of movement of said second lensunit.
 72. A zoom lens system with vibration reduction function accordingto claim 70, wherein said concave lens element is positioned mostadjacent to the object side in said second lens unit, and the followingcondition is satisfied:

    1.52<N-,

where N- is the refractive index of said concave lens element.
 73. Azoom lens system with vibration reduction function according to claim70, wherein said concave lens element is positioned most adjacent to theobject side in said second lens unit, and the following condition issatisfied:

    0.1<f2-/f2<0.7,

where f2- is the focal length of said concave lens element.
 74. A zoomlens system with vibration reduction function according to claim 70,wherein said second lens unit is fixed during the focal-length changefrom the wide angle end to the telephoto end.
 75. A zoom lens systemwith vibration reduction function according to claim 70, having a flarestop disposed on the image side of said second lens unit, said flarestop being fixed with respect to the direction across the optical axis.